产志贺毒素2k新亚型大肠埃希菌分子流行病学研究

产志贺毒素大肠埃希菌（Shiga toxin-producing Escherichia coli, STEC）是一类重要的动物性病原菌。志贺毒素（Stx）是STEC最重要的毒力因子，不同志贺毒素型或亚型与宿主来源及致病性密切相关。最近我们在STEC监测中发现和命名了一种中国特有的志贺毒素新亚型Stx2k，其出现机制及在人群中的传播风险尚不清楚。本项目拟系统地调查Stx2k新亚型STEC在中国人群、不同宿主动物和食品中的流行情况及分析菌株分子特征；分析不同Stx2k菌株的毒力及影响毒力差异的因素；从Stx2k前噬菌体的角度，揭示其遗传多样性及其对志贺毒素表达水平的影响；Stx2k噬菌体转染其他致病性大肠埃希菌从而导致新型高致病性菌株出现的可能性；探讨Stx2k新亚型STEC菌株出现的机制、菌株遗传进化规律、在不同宿主之间的传播途径以及感染人群的风险。

Shiga toxin-producing Escherichia coli (STEC) is an important zoonotic pathogen. Shiga toxin (Stx), the key virulence factor, can be classified into two types and several subtypes, which differ in host specificity and pathogenicity. We recently reported a novel Stx2k subtype which is exclusively identified in China so far. The emergence mechanism and transmission risk among humans remain unknown. In the current project, we will investigate the prevalence of the novel Stx2k subtype in humans, animals and foodstuffs in China. The molecular characteristics of Stx2k-STEC strains will be analysed. We will evaluate the virulence of Stx2k-STEC strains and underly the factors associated with distinct virulence capacity. We will assess the diversity of Stx2 prophages and its impact on Stx2 production. Since Stx-prophages can infect and lysogenize almost all E. coli pathotypes, we will assess the transfection ability of Stx2k phage, and possibility of emergence of new and enhanced virulent hybrid strains by Stx2k phage transfection among other E. coli pathotypes. We will further explore possible emergence mechanism of new Stx2k-STEC strains, evolutionary pattern, transmission route among different hosts, and the risk of human infection.